The invention relates to fruit and vegetable sizing. More specifically, the invention relates to reorienting a piece of fruit or a vegetable along a particular axis and then determining the size of the piece of fruit or vegetable using sound waves.
Sizing and sorting fruit and vegetables is labor-intensive, and thus expensive. Different devices for sorting and sizing fruit are summarized in "Automated Inspection/Classification of Fruits and Vegetables" by Dr. W. M. Miller, Transactions of the 1987 Citrus Engineering Conference, sponsored by the Florida Section of the ASME (Vol. XXXIII, pp. 42-52, Mar. 26, 1987); "Automated Density Separation for Freeze-Damaged Citrus" by W. M. Miller et al., Applied Engineering in Agriculture, (Vol. 4, No. 4, pp. 344-348, 1988); "Computer-Based Inspection of Freeze-Damaged Citrus" by W. M. Miller et al., ASAE Paper 86-6554 (December 1986); and "Mechanical and Physical Properties for Postharvest Handling of Florida Citrus" by W. M. Miller, Proc. Fla. State Hort. Soc., (99:122-127, 1986).
In order to reduce the complexity and cost of a fruit or vegetable sizer, measurements in two dimensions are frequently used to estimate the three-dimensional volume of a fruit or vegetable. Unfortunately, since fruit or vegetables are frequently irregular or non-spherical in shape, the use of only two dimensions to estimate the volume results in errors in the volume calculation. These errors in the volume calculation would be introduced in any calculations which depend on volume information, such as density calculations.
A method of reorienting fruit such that the major, intermediate, and minor axes of the fruit are oriented in predetermined directions, prior to being presented to dimension determining sensors, would minimize errors in volume calculation. Reorienting the fruit would also make the mechanical handling of the fruit less troublesome. In addition, reorienting the fruit would provide more accurate size sorting since size sorting is conducted according to the largest dimension of the fruit.
U.S. Pat. No. 4,380,294, issued to Morris on Apr. 19, 1983, discloses an apparatus for sorting fruits according to size. This device uses two belts moving at different speeds to reorient fruit. Unfortunately, this two-belt arrangement is mechanically complicated.
U.S. Pat. No. 4,091,931, issued to Button et al. on May 30, 1978, discloses a fruit-sorting apparatus which uses rollers to facilitate the positioning of tomatoes in pockets. This apparatus does not positively reorient fruit along a desired axis.
A method of ascertaining a particular dimension or other information regarding a piece of fruit involves the use of optical devices such as a line scan camera. Optical sensors are disclosed, for example, in U.S. Pat. No. 4,726,898, issued to Mills et al. on Feb. 23, 1988, and U.S. Pat. No. 4,122,951, issued to Alaminos on Oct. 31, 1978. Unfortunately, optical devices are expensive and tend to be troublesome in the harsh environments in which sizers must operate since optical devices must be kept clean in order to function properly. The level of cleanliness required for optical devices is difficult to maintain in a packing house.
Sound has been used in various sorting or sizing operations. For example U.S. Pat. No. 774,840, issued to Turner on Oct. 4, 1988, discloses a system for detecting the height of a stream of cigarettes using sound. U.S. Pat. Nos. 4,576,286, 4,557,386, and 4,690,284, all issued to Buckley et al., disclose sorting parts using acoustic energy. U.S. Pat. No. 3,435,950, issued to Suverkrop on Apr. 1, 1969, discloses a material separation device which uses sound to determine whether an object is a potato or a clod of dirt. U.S. Pat. No. 4,249,660, issued to Woodland on Feb. 10, 1981, uses sound to identify voids in potatoes. U.S. Pat. No. 3,254,888, issued Jun. 7, 1966 to Street, discloses a device which uses sound to determine if sheets of paper are overlapped. None of these patents disclose a simple device for determining the size of fruits or vegetables using sound.